Welcome to my world friend

Until FFG comes out with an errata that addresses this, decide in your local groups how you're going to play out this situation and make sure to get it clarified before any tournament.

That's going to be the easiest way to resolve the issue without an errata.

This is so true

The rules contain no instructions to check possible ship placement along each individual speed up to the final position.

Because the rules don't contain those instructions you can't assert that a ship should be destroyed if at a lesser speed it would be placed off the board, because you are given no ability to actually check if that were true (the ship being off the board) while completing a maneuver.

Simply put you are never putting the ship in the possible placements the lower speeds would allow thus you never have an instance where the ships base is out of the play area, unless that is the final position.

We have reached a full circle on this one

It will be interesting to see how FFG clarifies this.